When a watercraft, for example a speed boat, is driven over water, it will generate spray. Such spray can be disadvantageous. Other water users, such as swimmers or fishermen may suffer from the spray and any water skiers towed behind the craft may have their vision impaired. There are also environmental reasons to minimise spray; for example excess spray implies wasted energy.
Amphibious vehicles face difficulties not faced by watercraft in reducing spray. These problems arise from the presence of wheel arches defined in the vehicle hull. In the prior art (e.g. U.S. Pat. No. 4,958,584) amphibious vehicles have been provided with panels which close the wheel arches when the vehicle travels on water. However, it has been found that the opening and closing mechanisms for such panels are prone to mechanical failure due to the ingress of dirt and also due to corrosion. Therefore it has been preferred to have wheel arches which are open on water. However, such wheel arches are substantial discontinuities in an otherwise smooth hull lower surface and therefore generate spray which would not be generated by a smooth boat hull.
The present invention provides an amphibious vehicle having a hull and at least one rear wheel arch provided in the hull at the rear thereof, wherein the at least one rear wheel arch has a recess defined in a rear surface thereof, the rear surface being the surface of the wheel arch nearest to the rear of the vehicle, the recess acting as spray control means when the amphibious vehicle is travelling on water by channelling in a desired direction spray generated by interaction of the wheel arch with the water over which the vehicle is travelling.
Preferably, at least two rear wheel arches are provided in the hull at the rear thereof. Preferably, the rear wheel arches are provided in opposite sides of the hull.
The use of recesses as spray control means reduces the spray displaced outwardly by the vehicle by directing the generated spray in a different direction. Preferably the recesses direct the spray under the rear of the vehicle. Preferably this is achieved by each recess being a recess formed in the bottom surface of the hull extending rearwardly from and opening onto the rear surface of the respective wheel arch.
It is advantageous that the recess provided in the bottom surface of the hull tapers rearwardly from a respective wheel arch. In one embodiment, each recess is substantially semi-circular in a transverse cross-section.
It is preferable that each recess has a mouth region adjacent the rear surface of the respective wheel arch and a spray rail extending around the mouth region. This spray rail prevents spray recirculation forwards into the wheel arch.
The use of substantially linear spray rails on boat hulls is known. In this case, however, the spray rail is formed as a convex rib curved tightly around the mouth of the recess, smoothly blending into the wheel arch as shown in the accompanying drawings.
Preferably, the rear surface of each rear wheel arch has an edge region which extends around each recess to define a lip of the recess, the edge region being at least in part curved to encourage flow of spray into the recess. Each rear wheel arch may extend transversely inwardly from an outer arched edge linking said wheel arch to the vehicle outer bodywork to an inboard surface lying inwardly of a vehicle wheel, and preferably the edge region extending around each recess is curved at least in the part thereof nearest the outer arched edge of the wheel arch. This is the critical area for encouraging flow of spray into the recess. Preferably the outer arched edge of each wheel arch is curved at least in part thereof in a direction extending transversely inwardly towards the inboard surface of the wheel arch.
Preferably the amphibious vehicle is provided with wheel extension and retraction means operable to move a rear wheel located in each rear wheel arch between a lowered position for road use of the vehicle and a raised position for use of the vehicle on water.